A per-pixel multi-field motion adaptive deinterlacer keeps a record of several fields of pixels to successfully measure motion and correctly adapt the output deinterlaced pixel based on that measure of motion. The field type (TOP/BOTTOM) is taken into account to ensure valid motion values. Visually annoying artifacts will result if a TOP field is supplied in a situation when a BOTTOM field is expected (and vice versa).
Trick modes are, for example, pause, slow motion, fast forward, fast reverse, etc., anything other than standard linear playback. During linear playback, a system can rely upon a regular sequence of alternating TOP and BOTTOM fields. There may be a situation where the sequence may momentarily not alternate. A situation where the sequence momentarily does not alternate such as, for example, a TOP field followed by another TOP field, will be a rare occurrence and can be considered an error condition. When such an error condition occurs, a method of artifact mitigation is a suitable course of action.
Repeated field types, or even identical repeated fields, are common during trick mode operation. The same method of artifact mitigation, although possible, would produce lesser quality trick mode video than would otherwise be possible.
There are several methods to reduce errors associated with trick mode operation. One method of performing trick modes without a deinterlacer would be to use a scaler to invert field types. A problem with such a method is causing up and down jittering of horizontal lines and other areas of high vertical detail. A second method of performing trick modes without a deinterlacer would be to use only one field type from the source such as, for example, using TOP fields only or BOTTOM fields only. Using this method produces no up and down jittering, but does reduce vertical resolution, in addition to reducing temporal resolution, which makes a video look more “jerky.” Performing trick modes without a deinterlacer can be problematic because they require disabling and re-enabling the deinterlacer when entering and subsequently leaving trick mode, which can be awkward and would require software effort to ensure clean transitions.
Alternatively, errors can be reduced using methods that perform trick modes with a deinterlacer. One method would be to repeat fields at the input of the deinterlacer, and the deinterlacer drops back into spatial mode only and ignoring temporal information. Using this method causes up and down jittering of horizontal lines and other areas of high vertical detail.
The system may not suffer from awkward software control that may arise when it enters and leaves trick modes as video may still be passing through the deinterlacer. In a second method, the regular alternating field types at the input to the deinterlacer may be maintained and captured to memory after the deinterlacer. The second method may require at least twice the memory bandwidth with equivalent performance. Since memory bandwidth is finite, the use of other features in the system may be precluded.
Further limitations and disadvantages of conventional and traditional approaches will become apparent to one of skill in the art, through comparison of such systems with some aspects of the present invention as set forth in the remainder of the present application with reference to the drawings.